1. Field of the Invention
Device, methods, and systems consistent with the present invention generally relate to a signal generator, a signal generation method, and a radio frequency (RF) communication system.
2. Description of the Related Art
Typically, a spread spectrum communication signal is transmitted by spreading the signal over a bandwidth much wider than the bandwidth of the signal to be transmitted. The spread spectrum communication includes a method using a carrier of narrow-band having a certain cycle, such as code division multiple access (CDMA), and a method using a carrier of broadband.
The method using the narrow-band carrier modulates the frequency to make a frequency band of information to transmit narrower than the frequency band of the carrier. The method using the broadband carrier modulates the frequency to make a frequency band of information to transmit wider than the frequency band of the carrier.
The carrier adapted for spread spectrum communication, mainly, uses sine wave, pulse and the like. The carrier such as a sine wave or a pulse, needs to raise to a specific frequency to transmit data. To this end, in a communication system, a transmitter requires constituent elements for up-converting the data from the baseband to a specific frequency, and a receiver requires constituent elements for down-converting the data having the raised frequency to the baseband.
The transmitter includes a voltage controlled oscillator (VCO) for generating a frequency required for the data transmission, and a phase locked loop (PLL) for preventing the frequency generated at the VCO from being changed by external influences. The transmitter requires an up-mixer for up-converting the baseband data to the frequency generated at the VCO.
By contrast, the receiver, which receives an RF signal, requires a down-mixer for down-converting the carrier to baseband.
However, when the transmitter has the VCO, the PLL, the up-mixer and the like, a great amount of power is consumed and the up-mixer of a large size causes an increase in the size of the transmitter. Likewise, as the receiver also must use the down-mixer, its power consumption is considerable and its size is increased.
The IEEE 802.15.4a standardization group, which is a location-aware and power-efficient sensor network standardization group, currently is studying a next communication area by adding the location-awareness and power-efficiency functions to the mixed technology of the IEEE 802.15.4 (ZigBee) and 802.15.3 ultra wide band (UWB) standards.
To implement the power-efficiency function, a chaotic signal modulation is suggested. The chaotic signal modulation can be designed in hardware using a simple RF structure and does not require circuits such as VCOs, PLLs and mixers for the RF communication system. Accordingly, when the chaotic signal modulation is applied, the power consumption can be reduced to about one-third of the conventional power consumption, that is, to about 5 mW.
Hence, various designs have been suggested to enable the implementation of an RF communication system using chaotic signal modulation. The implementability of the system depends on the design of a chaotic signal generator which generates a chaotic signal.
Therefore, a demand exists for a method of designing a chaotic signal generator which can be easily implemented in an RF communication system using chaotic signal modulation.